This invention relates to a cathode ray tube and in particular to a cathode ray tube comprising an envelope containing electrically operable components comprising at least means for producing an electron beam within the envelope, electrical leadthrough means extending through the wall of the envelope, and conductor means extending within the envelope and electrically coupled between the leadthrough means and terminals of the electrically operable components.
An example of such a tube is described in U.K. Patent Specification No. 1598888 corresponding to U.S. Pat. No. 4,268,712. In this tube, the envelope consists of a mild steel cone to which is sealed a flat, toughened glass faceplate. In addition to an electron gun for producing an electron beam, the envelope contains also a channel plate electron multiplier and, although not specifically described, an electron beam deflection arrangement for deflecting the beam across a screen carried on the faceplate in raster fashion. Electrical interconnection between the internal, electrically operable components of the tube and the outside is established by means of a multi-pin leadthrough with circuit connectors sealed in vacuum-tight manner in the wall of the mild steel envelope. In order to connect the internal components with the multi-pin leadthrough, individual sheathed metal wires constituting conductors have been used. These wires are connected at their other ends to terminals associated with the components.
This form of interconnection is not entirely satisfactory. With the example of tube mentioned, it will be appreciated that as a large number of electrically operable components are situated within the envelope, a correspondingly large number of wires are needed to connect these components with the leadthrough, and difficulties are experienced in positioning these wires so as not to interfere with operation of the tube. In the case of compact tubes where available internal space is reduced to a minimum, the problem of arranging the wires around the structures within the envelope is even greater and makes assembly of the tube a time-consuming task.
A further consideration is that in tubes of the aforementioned type it is convenient to assemble the internal components as a sub-unit which is subsequently inserted into the metal envelope prior to sealing the faceplate. This procedure becomes impractical when using conventional wiring techniques to connect internal components to a leadthrough as the latter is located within the metal envelope and access to form the connections with the wiring is inhibited by the presence of the sub-unit.
Another important consideration with cathode ray tubes is outgassing. A large number of individual wires can significantly increase the risk of problems occurring in this respect and the choice of wire and sheathing materials is limited.